Current standard rack configurations are measured in rack-units (RUs). For example, a blade server may have a rack unit measuring 19 inches wide and having a pitch of 1.75 inches in height. A common computer rack form-factor is 42 RU high, which is a factor in limiting the density or number of components directly mountable into a rack. Higher density component systems are desirable since they require less space per rack enclosure and ultimately less space within the building housing the enclosures. Often these buildings must include high price high maintenance false floors to accommodate the mass of cabling and the delivery of chilled air and power to the enclosures. Another factor in determining component density is the pitch of the rack unit as often limited by the space required for component heat sinks and associated cooling components (e.g., fans).
Of particular concern is the cooling of the rack's components. During operation, the electrical components produce heat, which a system must displace to ensure the proper functioning of its components. In addition to maintaining normative function, various cooling methods, such as liquid or air cooling, are used to either achieve greater processor performance (e.g., overclocking), or to reduce the noise pollution caused by typical cooling methods (e.g., cooling fans and heat sinks). A frequently underestimated problem when designing high-performance computer systems is the discrepancy between the amount of heat a system generates, particularly in high performance and high density enclosures, and the ability of its cooling system to remove the heat uniformly throughout the rack enclosure.